big bore 85.5mm 62t/61x info

[Robbie8984]

Hi Guys,
Just got this motor of a mate and don’t know anything about it.

Anyone shed any light on it?

Bore is 85.5 mm

pistons say 65u 1.50 on them

looks like the piston has been hitting the dome on the exhaust port side. Domes only measure 84.5mm. All feels very sloppy so guessing it being worn bearing and to small a dome has done that?

 

[Robbie8984]

I’ve just measure the stroke at 68mm so is that a stock 701 crank in it?

 

[MTRHEAD]

68 is the 61x/62t stock stroke

 

[Robbie8984]

Anyone know if this can go to 86mm? Looks like the landing on the dome will be very thin if i machine it out to that?

 

[bored&stroked]

If its oem sleeve then no, you cannot do 86mm bore

 

[joelake]

Would an OEM sleeve do an 85.5mm bore? I thought 84mm was max for a 701.

What's with the piston hitting dome?

 

[Robbie8984]

Would an OEM sleeve do an 85.5mm bore? I thought 84mm was max for a 701.

What's with the piston hitting dome?

Yep 61x std sleeve is max 84mm. This has already had big bore sleeves fitted. Currently 85.5 mm pistons but is a bit worn out…

Im not convinced the guy who built it new exactly what he was doing… the dome is a machined 84.5mm 760 dome but they didn’t open it up to 85.5/86 so it looks like it’s been clipping the dome…

 

[88kawi5fiddy]

Yep 61x std sleeve is max 84mm. This has already had big bore sleeves fitted. Currently 85.5 mm pistons but is a bit worn out…

Im not convinced the guy who built it new exactly what he was doing… the dome is a machined 84.5mm 760 dome but they didn’t open it up to 85.5/86 so it looks like it’s been clipping the dome…

im not seeing where piston or dome is getting hit??

i see salt water corrosion on the OUTSIDE of the dome though.

the porting looks a lil rough but probably runs way better than the stock occluded ports the 61x is infamous for.
personally i'd clean it up and gasket it, and run it.

 

[long beach local]

I’d probably clean it up and run it too. Lol check the squish? Looks like it ran that way for awhile. Cranks not rusty

 

[bored&stroked]

Im not convinced the guy who built it new exactly what he was doing… the dome is a machined 84.5mm 760 dome but they didn’t open it up to 85.5/86 so it looks like it’s been clipping the dome…

You can run up to an 83mm bore on an oem 81mm cylinder head, so the domes on your setup should not be a problem.

 

[Robbie8984]

It’s quite hard to see from the pics but the chamfer on the front of the piston is where it’s been hitting the edge of the dome.

Ive not pulled crank yet but you can feel the play in the piston so maybe it’s was about to go bang and the play let it hit the dome.

 

[Robbie8984]

im not seeing where piston or dome is getting hit??

i see salt water corrosion on the OUTSIDE of the dome though.

the porting looks a lil rough but probably runs way better than the stock occluded ports the 61x is infamous for.
personally i'd clean it up and gasket it, and run it.

The rear piston has been hitting more than the front. The dome and piston have both chamfered them self where it’s been hitting on the exhaust port side of the piston.